Tenneco entered the Clean Air business in the mid-1970s, with the introduction of catalytic converters to passenger cars, driven by the Clean Air Act of 1970. This initial act led, in subsequent decades, to a series of regulations and amendments that imposed stricter emissions standards and broadened coverage from gasoline-powered passenger vehicles to include diesel trucks and other machinery employed both on- and off-highway.
This regulatory evolution sparked the corresponding development of increasingly sophisticated technology to control emissions at prescribed levels, which has enabled Tenneco to expand its emissions control business beyond light vehicles. Today, Tenneco supplies diesel aftertreatment systems to leading global manufacturers of engines and commercial equipment for companies that include Caterpillar/Perkins, John Deere, Deutz, Scania, MAN, and Kubota.
At present, off-highway vehicles are gearing up to comply with global regulations such as Tier 4 Final and EU Stage 4 to control criteria emissions including both particulate matter (PM) and nitrogen-oxide (NOx) emissions. For Tenneco, this means supplying customers with aftertreatment systems that meet these standards while overcoming four principal technological challenges:
• Function effectively at low temperatures. Off-highway vehicles typically operate at lower temperatures than on-highway trucks. Low-temperature operation can lead to the formation of urea deposits, causing the aftertreatment system to run less efficiently. We employ sophisticated predictive tools to design a combination of advanced mixing technology, thermal controls, and injector spray patterns to minimize the formation of deposits and assure optimized usage of reductant.
• Recognize price sensitivity. Manufacturers of smaller engines (7-L and below) are especially conscious of the costs associated with diesel aftertreatment systems, and may be less receptive to the same systems designed for on-highway heavy-duty trucks. Tenneco has succeeded in developing cost-effective solutions that meet off-highway requirements with Tier 4 Final systems that are in some cases actually lower in cost than the interim systems that preceded them. Tenneco’s turnkey system solutions, which offer one-stop shopping for catalysts, dosing, software, and electronics, allow manufacturers to reduce their development costs as well as variable costs.
• Achieve fuel economy. There is a recognized trade-off between fuel economy and engine out NOx emissions. Higher rates of NOx conversion in the aftertreatment allow engine calibration to reduce fuel consumption. Our diesel aftertreatment systems are able to achieve NOx conversion levels of up to 95% while enabling manufacturers to calibrate engines for maximum fuel economy. We resolve the trade-off through skillful integration of aftertreatment systems to provide optimized thermal management and flow uniformity, while accommodating the lowest possible backpressure.
• Meet durability requirements. Off-highway manufacturers require aftertreatment systems to operate effectively for useful lives between 8000 and 20,000 hours, or the equivalent of roughly one million miles. Utilizing the knowledge gained from developing multiple generations of diesel aftertreatment systems, Tenneco is building robust systems to meet these durability requirements.
Tenneco’s XNOx selective catalytic reduction system demonstrates the company’s capability to integrate individual components into effective systems that meet customer requirements ranging from 1.8-L light engines through +175-L large engines and address all of the principal technological challenges above. Our diesel aftertreatment incorporating urea dosing systems have been in production since 2009.
Looking ahead, we are already preparing for the next generation of clean air regulations— particularly those aimed at small engines such as those in the under 75-hp (56-kW) range, which had been excluded from the tightest NOx regulations. Tenneco has already designed aftertreatment systems that meet the unique performance and packaging requirements necessary to bring these smaller engines into compliance.
Moreover, Tenneco is committed to having turnkey technology in place to meet other future regulatory requirements, including increased onboard diagnostics in the off-highway environment.
Regulations will continue to evolve, and Tenneco is committed to be ready with both the technologies and the ability to integrate systems that enable our customers to comply effectively and economically in the future, as we have in the past.
Tim Jackson, Executive Vice President, Technology, Strategy, and Business Development, Tenneco Inc., wrote this article for SAE Off-Highway Engineering.